1. Field Of The Invention
This invention relates to measurement signal sources and in particular to an apparatus and a method of measuring the time relationship of two signals from different signal sources coupled into different points on a transmission line without knowing the physical distance between the signal source and the measurement device or the propagation delays of the transmission line.
2. Description of The Prior Art
Prior art measuring devices primarily consisted of apparatus for measuring unknown network parameters or transmission media discontinuities using a known signal source. Among these are time domain reflectometry devices, frequency domain reflectometry apparatus, and network analyzers. In such apparatus the measurement of unknown signal sources is affected by the transmission line or network through which it is passing and the distance between the signal source and the transmission line as well as the distance between the measuring device and the transmission line. General reflectometry measurement type devices are shown in U.S. Pat. Nos. 4,230,982 and 4,440,985. None of these prior art devices can measure the relationship of two signals applied at different points on a transmission line without knowing the propagation delays of the line.